A veteran member of Prime Minister Benjamin Netanyahu's Likud party may be tasked by the state comptroller with deciding the fate of an investigation into Netanyahu's alleged double billing of trips abroad.

State Comptroller Joseph Shapira is said to be leaning toward sending the findings to Knesset Speaker Reuven Rivlin of Netanyahu's Likud party, after several legal opinions submitted to Shapira - including one by Netanyahu's personal lawyer, David Shimron - argued that ethical lapses by MKs are the province of the Knesset Ethics Committee, not the comptroller. Rivlin would decide whether to hand the matter over to the committee.

Netanyahu was an MK, not a cabinet member, when he took the trips in 2006, three years before becoming prime minister.

Rivlin could decide to shelve the issue, on the grounds that too much time has elapsed since the alleged improprieties took place. But even if he does send the material to the ethics committee, the panel is considered unlikely to take up the issue, given the long time that has elapsed and the difficulty of getting full information about the trips from the people or agencies that reportedly financed them.

Alternatively, Rivlin could ask Attorney General Yehuda Weinstein to look into what has come to be known as the Bibi Tours affair.

Shapira is said to be leaning toward omitting the double-billing allegations from his next report on the grounds that the comptroller has no authority to investigate Knesset members who are not cabinet members.

Staffers from the comptroller's office questioned Netanyahu twice this year about the trips he and his wife, Sara, took abroad, as part of the comptroller investigation.

If Shapira had concluded that Netanyahu's conduct raised suspicions of criminal behavior, he would be expected to transfer the material to Weinstein, which he has not done. Some of the staffers who worked on the probe have suggested that Shapira should send it to the attorney general and let him decide whether it warrants a criminal investigation.

Shapira is considered most likely to send the findings to Rivlin if he does not include the trips in the report or send the investigative material to Weinstein.

A draft of the comptroller's report will be distributed in several weeks to the subjects of the investigation, and Shapira is slated to make a final decision next week on whether to include Netanyahu's trips in the report.

"Shapira is currently studying the matter," the comptroller's office said in a statement. "As per standard practice in the comptroller's office, draft [chapters] will soon be sent to those criticized in them for their comments. We stress that we have no intention of shelving the report."

According to investigative reports broadcast by Channel 10 television in March and April, 2011, the Netanyahus received funding from two different sources to cover the same trip abroad in September 2006. The reports also cited another instance of alleged double billing in August 2006, when the Netanyahus and one of their sons went to London to speak on Israel's behalf during the Second Lebanon War. According to Channel 10, that trip was funded by both the Knesset and Israel Bonds.

Channel 10 also said that even after he returned to the Knesset in 2003 after a four-year absence, Netanyahu and his wife sometimes had their overseas flights paid for by private individuals or organizations.

Netanyahu has flatly denied all the allegations, and his attorney submitted a variety of documents and receipts to the comptroller in an effort to prove he had done nothing wrong.

Shapira's predecessor, Micha Lindenstrauss, set up a special task force to investigate the alleged improprieties after the Channel 10 reports were aired. In response to pressure from coalition parties, Lindenstrauss later expanded the mandate of the investigation to cover all overseas trips by ministers and deputy ministers since 2006.

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